How to Gamma Cross of Multiple Strips?
I realize this is ancient but I'm replying anyway because I had the same problem and figured out a solution.

Instead of making a gamma cross of multiple strips, just make two different gamma crosses, one for your text layer + color strip, one for your image layer + color strip. Worked great for me!

Best of luck!

MalcolmRoseGM

Edit: I've been asked to include a screenshot. Here is what my example looks like: 

So basically this whole contraption makes an outro where I have some text on the screen ("continued in part x"), a little demon guy who rotates, then both the text and the demon guy fade out and a short outro video plays. What we're concerned with is the fadeout.

Please note in the picture that I've first made a gamma cross with the "part2.0" strip + the black color bar, then I made another gammacross with "Transform.002" strip and the black color bar. The first is the image file that contains the text on a transparent background, the second is an image file which contains the demon image (the transform strip is only necessary because I wanted to offset it to the left. I assume you are doing something similar).

This entire effect probably could have instead been done with one gamma cross if I had just, say, combined the images in an image editor but I didn't want to do that since I was already doing transformations and things. Again, I assume you are doing something similar!

The end result looks like the outro at the end of this video: https://www.youtube.com/watch?v=GJFsKE2jqYU&amp;t=1h54m50s

Hope this helps!